From the State of the Art, torsion measuring systems for measuring torsion between a first measuring point and a second measuring point of a test object are known. In the published patent application DE 10 2010 005 665 A1, the distance between the first and the second measuring point is connected by an optical fibre. A light source is coupled to the optical fibre directly in the first measuring point which emits polarized light. Directly in the second measuring point, a polarization analyzer is coupled to the optical fibre. Torsion of the test object by incorporating the optical fibre between the measuring points causes rotation of the polarization plane of the light which has been irradiated into the optical fibre by the polarizing light source.
From the publication CN 203 704 884 U, a fibre-optic torsion sensor formed in an embedded design is known. The embedded design permits a torsion measurement over a measuring section of 1 m max.
When a conventional fibre-optic torsion sensor is used in order to determine torsion over a larger measuring section of a test object, it sometimes happens that the sensor fibre in addition to torsion is also subject to bending. This may happen, for example, when the sensor fibre for measuring torsion is used on a curved test object, for example, a lightweight structure of a building or the like.
Bending of the sensor fibre results in a measurement uncertainty and/or a measuring error in conventional torsion sensors. Therefore, it is desirable to provide an apparatus or method for measuring the torsion of a test object in which measurement accuracy is improved.